In restaurants, it may be advantageous to recover energy, using heat exchangers, from the hot air that may be ordinarily exhausted from the restaurant kitchen. It may also be advantageous for such a restaurant to extract grease from the hot kitchen exhaust air, preferably before attempting to recover heat energy from the exhaust air. As both processes may involve operations performed on the hot exhaust air, it may be particularly advantageous to generally combine both processes into one system.
In the prior art, the recovery of heat energy from kitchen exhaust air has been notoriously inefficient—at least in part because of the high grease content of the air which is exhausted from restaurant kitchens. It is, perhaps in large part because of these inefficiencies, that many have sought to improve the methods by which grease might be removed from the exhausted kitchen air before reaching a heat exchanger. Notably, however, the previous attempts to “degrease” kitchen exhaust air have given rise to significant problems of their own, in each of the varied, numerous and highly complex, ineffective, and/or hazardous devices which may have been previously employed for such purpose. Such prior art heat exchangers may have been generally classified into three different groups: (i) those employing chemical degreasing means, (ii) those attempting to degrease exhaust air using a complex system of filters and/or convoluted air flow conduits, and (iii) those which simply make use of an angled baffle together with an underlying grease trap.
Of course, it may be readily apparent that the use of chemicals to degrease exhaust air presents certain hazards to those who may be periodically charged with cleaning or otherwise servicing the heat exchangers. With reference to the use of filters and convoluted air flow conduits, on the other hand, it is generally believed, though not essential to the working or utility of the present invention, that such conduits and filters may significantly reduce the amount of energy remaining available for reclamation in any exhaust air which may, after passage through such structures, reach a heat exchanger. Accordingly, heat exchange devices in the second general grouping identified above may be substantially inefficient and/or may tend to result in a lower rate of energy transfer, such that restaurants employing same may not realize a significant savings in heat consumption. Additionally, it is generally believed, though not essential to the working or utility of the present invention, that restaurants using simple baffle and grease trap systems may typically have found such systems insufficient to remove any substantial amount of grease from the kitchen exhaust air.
It is noted that some previous heat exchanging devices may have included fans to draw grease-laden exhaust air from the restaurant kitchen. In the vast majority of these known heat exchange systems, however, the fans have even been positioned downstream of the heat exchanger, so as to draw the hot exhaust air therethrough. Such previous heat exchange systems have, notably, suffered from serious disadvantages, at least insofar as any kitchen exhaust air reaching the heat exchanger may have still been heavily laden with grease. As a result, grease in the exhaust air may have highly diminished the efficiency of the heat exchanger, and may heretofore have tended to accumulate as a coating over virtually all of the components, including the inner workings of the hear exchanger. Accordingly, such previous heat exchangers, grease “traps”, and/or other grease removers may have previously required laborious cleaning on a regular basis. As may be appreciated from the foregoing, failure to clean these previous heat exchangers and their surrounding components may have typically resulted in a much lower efficiency in terms of energy transfer, with a correspondingly diminished savings in the restaurant's energy expenses.
While some previous heat exchange devices may have included heat exchange coils positioned downstream of the fans, such fans have not heretofore been used to remove grease from exhaust air. Moreover, fans previously disclosed for use in heat exchange systems would not have been effective to remove grease from exhaust air, due perhaps in part to the types of fans employed (e.g., axial flow fans) and/or to the slow fan rotation speeds. Accordingly, fans have not previously been used, in the field of restaurant heat exchangers, to degrease kitchen exhaust air. Rather, persons of ordinary skill in the art may heretofore have believed it necessary to utilize other de-greasing means which may be generally classified in one of the groups identified above.
It is, at this stage, perhaps worthwhile to also note that, there is another reason why many fans previously utilized in heat exchangers may not have been suitable for use in restaurant kitchen exhaust air heat exchangers, namely, because such use may give rise to significant safety concerns. That is, the fans in many previous heat exchangers have included fan motors which may heretofore have been disclosed as being positioned within the air flow path. It is generally thought, though not essential to the working or utility of the present invention, that the high heat and/or grease content that may typically be characteristic of restaurant kitchen exhaust air presents a certain fire hazard, which makes it unsafe to position an electric fan motor within the flow path of such exhaust. Accordingly, and despite any previous disregard for such concerns in the prior art, many previous heat exchangers that have included fans are neither safe nor suitable for use in association with restaurant kitchen exhaust air. In view of the foregoing, it should be appreciated that, quite apart from individuals concerned with other types of heat exchanging devices, persons having ordinary skill in the art have been required to specialize solely in the area restaurant heat exchangers as a unique field (with unique problems and concerns) unto its own.
Now, fans previously used in heat exchangers may have been adapted to spin at a user-selected speed, but any such ability to select a specific fan speed has heretofore been extremely limited—typically presenting only very limited options (e.g., two distinct and very specific speeds). While some previous fans may have been adapted to vary their speed in response to air temperature, such fans have not heretofore been used to remove the grease from kitchen exhaust air, nor would they have been effective for such use (due either to the types of fans being utilized and/or to the small range of slow speeds which may typically have been previously afforded by such fans). In order to particularly adapt a fan, in a restaurant heat exchanger, for use in removing grease from kitchen exhaust air, it would be advantageous to provide a fan that is capable of operating at high enough speeds to strip the grease from the exhaust air, whilst also being capable of varying its speed in direct response to the temperature of the kitchen exhaust air.
Apart from all of the above, it is important to recognize that prior art restaurant heat exchangers have only afforded users a minor degree of freedom in deciding how any heat recovered from kitchen exhaust air should be distributed. For example, after recovering heat energy from partially degreased kitchen exhaust air, some prior art heat exchangers may have provided for user-actuation of a three-way valve so as to enable selective distribution of the recovered heat energy between supply air and/or supply water to be returned to, or used within, the restaurant. Notably, the prior art does not disclose any means for efficiently and automatically activating and distributing the recovered heat energy in accordance with a restaurant owner's pre-selected priority schedule. In addition, the prior art has failed to address the need amongst restaurant owners for a greater degree of freedom and flexibility in deciding how any recovered heat energy should be distributed within the restaurant. Neither has the prior art offered an efficient and highly customizable method for prioritizing the delivery of recovered heat energy as between all of the following three (3) discrete systems which, according to the invention, are each recognized as being subject to their own unique heating demands in a restaurant: (a) supply air for delivery to the restaurant dining room, (b) hot water for use in the restaurant, and/or (c) makeup air for delivery back to the kitchen.
At this time, it is specifically noted that although attempts have been made, in the prior art, to develop efficient restaurant kitchen heat recovery systems, successful installations have not been documented.
Accordingly, there may be a need for an improved heat recovery system for use with restaurant kitchen exhaust air. Ideally, such a heat recovery system may be highly efficient at removing grease from restaurant's kitchen exhaust air, allowing recovered heat to be distributed as needed between the make-up kitchen air, the restaurant's hot water tank, and the restaurant's general eating area air supply.
In view of all of the foregoing, it may be particularly advantageous to provide a restaurant heat exchange system which includes a fan that is not only effective to substantially degrease the kitchen exhaust air, but also to push the largely degreased exhaust air downstream, substantially unimpeded, towards a heat exchanger that might then recover heat energy therefrom in a highly efficient manner. Such a system might most advantageously also enable greater flexibility and customization in determining how any recovered heat energy might be distributed within the restaurant. It is generally thought, though not essential to the working or utility of the present invention, that, such a system might result in a higher rate of energy transfer, in a higher overall efficiency, and/or in the ability to process of a high quantity of air. Additionally, the use of such a system might also afford a significant savings in terms of the restaurant's electricity and/or natural gas expenses.
It is an object of this invention to obviate or mitigate at least one of the above mentioned disadvantages of the prior art.